When Simian Virus 40 (SV40) infects a permissive monkey cell, a number of enzymes involved in DNA metabolism increase in activity, and both host and viral DNA synthesis is stimulated. The types and amounts of DNA polymerase present in SV40-infected cells are being examined by DNA cellulose chromatography. The enzymes present in infected cells are being compared to the enzymes of uninfected, resting cells and of uninfected actively growing, serum stimulated cells. These isolated enzymes are being characterized by their physical properties. When this characterization is complete, their function in an in vitro SV40 DNA replicating system will be examined, in an attempt to determine their function in SV40 replication in vivo. In addition, the effect of the drug cytosine arabinoside on both cell growth parameters and on the isolated DNA polymerase activities is being examined. These studies should indicate the site and mode of action of this drug. The cell growth data is being incorporated into a selection technique to isolate cytosine arabinoside resistant cell mutants. Some of these mutants should have alterations in their DNA polymerases, and these mutants will be useful in examining the mechanism of DNA synthesis and repair in mammalian cells.